1. Field of the Invention
The present invention, in the field of biochemistry, particularly relates to a method for imaging the saccharide uptake activity of living cells which are in a state of maintaining biological activity and for obtaining information relating to changes in viability of living cells with external stimulations.
2. Description of the Prior Art
It is considered that the most universal indicator for representing the viability of living cells is an energy source uptake activity (uptake rate or uptake quantity). The typical example what of many of those cells can commonly take up as an energy source is glucose. However, no useful imaging methods for the glucose uptake activity has been developed until now.
Heretofore, as a method for imaging the glucose uptake activity in living bodies or tissues thereof, a 2-deoxyglucose (2-DG) method has been conducted. Namely, it is a method in that after a radioisotope labeled 2-deoxyglucose is incorporated instead of glucose, slices of living bodies or tissues thereof are observed by mean of autoradiography. However, this method does not allow, the bodies or tissues to be imaged as they are alive at real time, and requires complicated operations and is, furthermore, not sufficient in spatial resolution.
On the other hand, as techniques for imaging living bodies as they are intact, an X-ray CT, PET, MRI, etc. have already been developed. However, though these can image three-dimensionally, any of them have only a spatial resolution of about 0.1 mm, so that a resolution at a single cell level cannot be obtained. Alternatively, with an X-ray microscope and an atomic force microscope, a resolution superior to an optical microscope is obtained. However, they can image only appearances and shapes. Therefore, there still are many technical difficulties for obtaining images corresponding to the glucose uptake activity.
In order to image living bodies or tissues thereof having bioactivity (referred to as "living tissues, etc." hereinafter) as they maintain the bioactivity, namely, when they are alive, and to obtain, in combination with a microscope, spatial resolution at a single cell level, many fluorescent reagents have so far been developed. For example, mention may be made of (1) those having a fluorescence intensity or fluorescence wavelength which change with changes in the calcium ion concentrations or pH, (2) those having fluorescence intensity which change with changes in the surface potentials of cells, (3) those having a different permeability of the cell membrane between living cells and dead ones, (4) those which emitting fluorescence upon decomposition by a specific enzyme only in living cells, and (5) those combined with antibodies (fluorescence labeled antibody). If these fluorescent reagents are used, though information relating to living or dead cells, or information about responsiveness to exterior stimulation is obtainable, the information is not always said to be a general and universal indicator showing the viability of the cells of the living tissues, etc.